Arrest at Sydney airport after Mick Hawi murder tip-off

Police arrested a young man at Sydney Airport less than 24 hours after the gangland slaying of former Comancheros boss Mahmoud "Mick" Hawi.

Acting on a tip-off, detectives from strike force Amirs arrested the unnamed 29-year-old on Friday February 16.

A day earlier, Hawi had been gunned down outside a gym in Rockdale, in Sydney's southeast.

The man was trying to board a flight at the time of his arrest.

Police allegedly found a loaded semi-automatic Desert Eagle pistol at his home in Hurstville shortly afterwards.

After being examined by specialist ballistic officers, police concluded the pistol was not the gun used in the shooting.

The man has not been charged in relation to Hawi's death, but according to the Daily Telegraph, he is being held at a Sydney hospital under mental health legislation.

Hawi, 37, was jailed for the 2009 killing of rival bikie Anthony Zervas at Sydney Airport.

He became the national president of the Comancheros when he was just 22.

Police are still investigating his murder.